Flue Gas Particle Characterization at Different Parts of the Power Plant · · 2013-09-14Flue Gas...
Transcript of Flue Gas Particle Characterization at Different Parts of the Power Plant · · 2013-09-14Flue Gas...
Flue Gas Particle Characterization at Different Parts of the Power PlantVille Niemelä, Erkki LamminenDekati Ltd., Tampere, Finland
A&WMA International Specialty Conference: Leapfrogging Opportunities for Air Quality Improvement May 10-14, 2010, Xi’an, China
© Dekati Ltd.
Introduction
• Power plants and coal combustion are major sources for fine particles
• This work focuses on particle measurements at power plant
• Particle characterization at plant allows – Understanding particle formation and transformation
– Optimization of combustion process
– Optimization and control of cleaning systems
In this work we present:
• Sampling system for power plant flue gas PM measurements– Sample dilution in different locations of the plant
– Controlled sample cooling and VOC control
• Measurement system for power plant PM measurements– Particle concentration and size measurement at power plant
environment
• Results for– Particle concentration and size distribution in the flame, after heat
exchangers and after baghouse filter
• Size distribution change
• Effect of baghouse filter cleaning system
• Discussion– About PM transformation
© Dekati Ltd.
Method 1: Sampling
• Temperature controlled probe– Heated and cooled with pressurised
air, 200 C
– Austenitic stainless steel for high
temp measurement
• P and T measurement after probe
• Heated sampling line, 200 C
• DEED – Two-stage dilution system
– Control / removal of VOC and water
© Dekati Ltd.
Dilution air
heater and
temperature
controller,
200°C
Heated SS sampling
line 200°c
ELPI DEED
T P
STACK
PA
Method 2: Dilution with DEED
• Three-stage dilution:– Heated dilution stage 1:10
reduces gaseous VOC
concentration without condensation
– Evaporation tube at 350°C evaporates already condensed VOCs
– Cold dilution stage 1:10 cools down the sample without condensation
– (Extra 1:10 dilution stage on/off)
© Dekati Ltd.
Outlet (sample to ELPI)
First dilution stage (PND 1)
with dilution ratio of 10
Dilution at 150°C
Second dilution stage
(PND 2) with dilution
ratio of 10
Dilution at ambient
temperature
Evaporation tube (ET) 350°C
Inlet
(sample from CVS) 2.5 micron cyclone (optional)
Pre-diluter with dilution ratio
of 1 or 10 (OFF or ON)
DEED Offers
• Two or three dilution stages plus evaporation tube
• High dilution ratios: 1:100 and 1:1000
• Controlled sample cooling with low losses
• Heated 1st stage and evaporation tube prevent VOC and other volatile material condensation
© Dekati Ltd.
ELPI offers
• Real-time particle size distribution 0.007/0.030 – 10 µm
• Real-time number concentration, estimation for mass
• Wide dynamic range - from ambient concentrations up to power plant levels
• Particles are collected - option for size-selected chemical /physical analysis
• Option for particle charge level measurements (ESP studies)
© Dekati Ltd.
Measurements:
• 4 MW pilot power plant in Finland
• Circulating Fluidised Bed combustion
• Wood pellets
• Baghouse filter
• Measurement locations:– Right after the flame, T=800 °C
– After heat exchangers, T=200 °C
– After baghouse filter
© Dekati Ltd.
Results 1: PM concentration
• Flame (hot location) has lower number concentration
• Mass concentration is the same
• Effect of soot blowing – decrease number, increase in mass (fine particle washout)
© Dekati Ltd.
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
3.0E+07
3.5E+07
4.0E+07
0 100 200 300 400
Nu
mb
er
con
cen
tra
tio
n [
1/
cm3
]
Time [s]
Number concentration
Hot
Cool
0
200
400
600
800
1000
1200
0 100 200 300 400 500
Ma
ss c
on
cen
tra
tio
n [
mg
/m
3]
Time [s]
Mass concentration
Hot
Cool
Results 2: PM size distribution
• Increase in number-based size (and concentration) when T decreases – dominated by small particles
• Mass distribution (coarse particles) remains the same except during soot blowing
• Bi-modal distribution (seen in surface area)
© Dekati Ltd.
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
3.0E+07
3.5E+07
4.0E+07
0.01 0.1 1 10
dN
/dLo
gDp
[1
/cm
3]
dp [um]
Number
Hot
Cool
Soot
blowing
0
50
100
150
200
250
300
350
400
0.01 0.1 1 10
dM
/d
Lo
gD
p [
mg
/m
3]
dp [um]
Mass
Hot
Cool
Soot blowing
0.0E+00
2.0E+05
4.0E+05
6.0E+05
8.0E+05
1.0E+06
1.2E+06
0.01 0.1 1 10
dA
/d
Lo
gD
p [
µm
²/cm
³]
dp [um]
Surface areaHot
Cool
Soot
blowing
Results 3: Baghouse filter
• Efficiency 90% for number, 92% for mass
• Drop in efficiency at about 100 nm
• Concentration after the filter 10.8 mg/m3
© Dekati Ltd.
0
20
40
60
80
100
120
0.01 0.1 1 10
Fil
trat
ion
eff
icie
ncy
[%
]
dP [um]
Filtration efficiency
Filtration
efficiency
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
3.0E+07
3.5E+07
4.0E+07
0.01 0.1 1 10
dN
/d
LogD
p [
1/
cm3
]
dP [um]
Baghouse filter
Before filter
After filter
Discussion
• Reason for small particle size change– Condensation? Agglomeration?
– Further chemical and SEM / TEM analysis possible
© Dekati Ltd.
Conclusions
• A system capable of measuring PM size distribution and concentration in real time at different parts of the power plant – anywhere from the flame to the flue gas exit
• Measurement shows clear change in particle size distribution when flue gas temperature decreases
• Size-resolved filtration efficiency for flue gas cleaning system
© Dekati Ltd.